U.S. Pat. No. 5,379,353 suggests a differential analysis circuit that utilizes a step to identify edge vectors for identification of such things as a road for a mobile robot. A digital image captured from a video camera is processed using an algorithm that includes generation of a differential of brightness along each row of pixels, and presumably also along each column of pixels. The absolute value of the differential brightness represents a change in the picture, and a differential that exceeds a threshold is identified as a possible edge to a road.
U.S. Pat. No. 5,381,155 suggests a speed detection system that identifies moving vehicles in the view of a fixed camera, measures the speed at which the vehicles are moving, and identifies a license plate number from the vehicle. Commercially available systems are disclosed that are said to be capable of identifying the license plate within a captured image and then reads the numbers and letters within the license plate number.
U.S. Pat. No. 5,381,489 suggests a system for recognition of characters on a medium. This system includes making a window of a possible character from the medium, and then comparing that window to each template within a set. The entire set of templates must be screened each time a character is identified. The templates are generated based on previously recognized characters from the document where the initial recognition requires a more rigorous comparison to different character features.
A problem faced in visual recognition is to recognize the location, within the view of a camera, and the orientation, of a particular article where the article may be one of a relatively few possible articles already identified from a library of potential articles. The possibility of a variety of lighting conditions and shadows make such recognition difficult. There are also typically constraints on the amount of computer data storage available at the site of a desired visual recognition facility. Therefore, templates of different orientations an scales of the different articles can generally not be generated and stored initially.
Such a problem in visual recognition is encountered when visual recognition is used as a means to identify vehicles or determine the orientation of vehicles in an automated refuelling system. For example, in U.S. Pat. No. 3,527,268 it is suggested that vehicle identification in an automated refuelling system can be achieved in a fully automated method by a photo-electric means to detect the silhouette of the automobile. How this is to be done is not suggested.
It is therefore an object of the present invention to provide a method to identifying the location and orientation of an article, wherein the method is capable of identifying the location and orientation of the article in a variety of natural and artificial lighting conditions, and wherein a large number of templates do not have to be digitally stored.